Fountain solution film thickness measurement system using Fresnel lens optical properties

ABSTRACT

An apparatus and method for measuring the thickness of fountain solution (FS) in a Digital Architecture for Lithographic Ink (DALI) printing system by transferring the FS to an optical roller with the properties of a lens and measuring the resulting effect on the refraction of an image captured through the lens. The optical roller may comprise a clear or glass cylinder forming a Fresnel lens cylinder having an engineered surface of known surface roughness and wherein the roller is placed adjacent the image member blanket. A heat source is used to evaporate the FS from the blanket for transfer to the optical roller where the FS wets the roller surface to different degrees based on the FS thickness relative to Fresnel ridge depth. Changes to the optical refraction through the lens varies with the FS thickness. An image sensor (e.g., a CCD camera or image analysis system) evaluates the image through the optical roller for FS thickness determination.

FIELD OF DISCLOSURE

This invention relates generally to digital printing systems, and moreparticularly, to fountain solution deposition systems and methods foruse in lithographic offset printing systems.

BACKGROUND

Conventional lithographic printing techniques cannot accommodate truehigh speed variable data printing processes in which images to beprinted change from impression to impression, for example, as enabled bydigital printing systems. The lithography process is often relied upon,however, because it provides very high quality printing due to thequality and color gamut of the inks used. Lithographic inks are alsoless expensive than other inks, toners, and many other types of printingor marking materials.

Ink-based digital printing uses a variable data lithography printingsystem, or digital offset printing system, or a digital advancedlithography imaging system. A “variable data lithography system” is asystem that is configured for lithographic printing using lithographicinks and based on digital image data, which may be variable from oneimage to the next. “Variable data lithography printing,” or “digitalink-based printing,” or “digital offset printing,” or digital advancedlithography imaging is lithographic printing of variable image data forproducing images on a substrate that are changeable with each subsequentrendering of an image on the substrate in an image forming process.

For example, a digital offset printing process may include transferringink onto a portion of an imaging member (e.g., fluorosilicone-containingimaging member, printing plate) having a surface or imaging blanket thathas been selectively coated with a fountain solution (e.g., dampeningfluid) layer according to variable image data. According to alithographic technique, referred to as variable data lithography, anon-patterned reimageable surface of the imaging member is initiallyuniformly coated with the fountain solution layer. An imaging systemthen evaporates regions of the fountain solution layer in an image areaby exposure to a focused radiation source (e.g., a laser light source,high power laser) to form pockets. A temporary pattern latent image inthe fountain solution is thereby formed on the surface of the digitaloffset imaging member. The latent image corresponds to a pattern of theapplied fountain solution that is left over after evaporation. Inkapplied thereover is retained in the pockets where the laser hasvaporized the fountain solution. Conversely, ink is rejected by theplate regions where fountain solution remains. The inked surface is thenbrought into contact with a substrate at a transfer nip and the inktransfers from the pockets in the fountain solution layer to thesubstrate. The fountain solution may then be removed, a new uniformlayer of fountain solution applied to the printing plate, and theprocess repeated.

Digital printing is generally understood to refer to systems and methodsof variable data lithography, in which images may be varied amongconsecutively printed images or pages. “Variable data lithographyprinting,” or “ink-based digital printing,” or “digital offset printing”are terms generally referring to printing of variable image data forproducing images on a plurality of image receiving media substrates, theimages being changeable with each subsequent rendering of an image on animage receiving media substrate in an image forming process. “Variabledata lithographic printing” includes offset printing of ink imagesgenerally using specially-formulated lithographic inks, the images beingbased on digital image data that may vary from image to image, such as,for example, between cycles of an imaging member having a reimageablesurface. Examples are disclosed in U.S. Patent Application PublicationNo. 2012/0103212 A1 (the '212 Publication) published May 3, 2012 basedon U.S. patent application Ser. No. 13/095,714, and U.S. PatentApplication Publication No. 2012/0103221 A1 (the '221 Publication) alsopublished May 3, 2012 based on U.S. patent application Ser. No.13/095,778.

The inventors have found that digital printing processes are sensitiveto the amount of fountain solution applied to the imaging memberblanket. If too much fountain solution is applied to the imaging membersurface, then the laser may not be able to boil/evaporate the fountainsolution and no image will be created on the blanket. If too littlefountain solution is applied to the imaging member surface, then the inkwill not be rejected in the non-imaged regions leading to highbackground. Currently, there is no way to measure how much fountainsolution is deposited on the imaging member blanket in real-time duringa printing operation. Further, current fountain solution systems operateopen loop, where the amount of fountain solution is manually adjustablebased on image quality of previous print jobs. In this state, fountainsolution systems are at the mercy of printing device noises and mayrequire constant manual adjustments.

Methods of measuring fluid thicknesses are taught in U.S. Pat. No.3,227,951 (Dykaar), “Electrical device for capacitively measuring thethickness of a layer of fluid” and in U.S. Pat. No. 7,953,332(Jeschonek), “Method for regulation of the optical density in anelectrographic printing method as well as a toner layer thicknessmeasurement system and electrographic printer or copier”. Despite thesemethods, there is still room in the art for improvement. In particular,it is desirable to provide the ability to measure the thickness of thefountain solution within the printer at a relatively low cost usingoptical methods.

SUMMARY

The following presents a simplified summary in order to provide a basicunderstanding of some aspects of one or more embodiments or examples ofthe present teachings. This summary is not an extensive overview, nor isit intended to identify key or critical elements of the presentteachings, nor to delineate the scope of the disclosure. Rather, itsprimary purpose is merely to present one or more concepts in simplifiedform as a prelude to the detailed description presented later.Additional goals and advantages will become more evident in thedescription of the figures, the detailed description of the disclosure,and the claims.

The foregoing and/or other aspects and utilities embodied in the presentdisclosure may be achieved by providing a method of controlling fountainsolution thickness on an imaging member surface of a rotating imagingmember in an image forming device. The method comprises (a) dispensingthe fountain solution from an applicator onto the rotating imagingmember; (b) positioning a transparent roller with a predeterminedroughness adjacent said rotating imaging member, the transparent rollercomprising an imaging device positioned within the transparent rollerfor capturing light passing through the surface, the surface forming alens and wherein light passing through the lens to the imaging device isdefined by a first set of optical properties; (c) transferring thedispensed fountain solution from said rotating member onto said surfaceof said transparent roller to allow said transferred fountain solutionto wet the surface of the transparent roller to alter the first set ofoptical properties to a second set of optical properties; (d) comparingthe second set of optical properties with the first set of opticalproperties to calculate a thickness of the dispensed fountain solutionon the transparent roller; (e) modifying the fountain solution dispenserate based on the calculated thickness; and (f) applying a subsequentfountain solution layer at the modified fountain solution dispense rateonto the imaging member surface for rendering a subsequent printing.

According to aspects described herein, an exemplary image forming devicecontrols fountain solution thickness on an imaging member surface of arotating imaging member. The image forming device comprises: a fountainsolution applicator configured to apply a fountain solution fluid layerat a dispense rate onto the imaging member surface in an image makingdirection for rendering a printing; a transparent roller having asurface of a predetermined roughness and where the transparent rollerfurther comprises an imaging device positioned within the transparentroller for capturing light passing through the surface, the surfaceforming a lens and wherein light passing through the lens to the imagingdevice is defined by a first set of optical properties; a heat sourcefor evaporating the dispensed fountain solution from the imaging memberto the transparent roller where the evaporated fountain solution thencondenses onto the transparent roller, the condensed fountain solutionwetting the surface to alter the first set of optical properties to asecond set of optical properties; a controller in communication with theimaging device to compare the first set of optical properties with thesecond set of optical properties to determine a thickness of thedispensed fountain solution on the transparent roller and in accordancetherewith to define a modified fountain solution dispense rate toprovide an optimum thickness of the dispensed fountain solutionthickness; the fountain solution applicator configured to apply asubsequent fountain solution layer at the modified fountain solutiondispense rate onto the imaging member surface for rendering a subsequentprinting.

Exemplary embodiments are described herein. It is envisioned, however,that any system that incorporates features of apparatus and systemsdescribed herein are encompassed by the scope and spirit of theexemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Various exemplary embodiments of the disclosed apparatuses, mechanismsand methods will be described, in detail, with reference to thefollowing drawings, in which like referenced numerals designate similaror identical elements, and:

FIG. 1 is block diagram of an image forming device in accordance withexamples of the embodiments and with the lead line arrow showing thelocation of the combination 100;

FIG. 2 is a perspective view of an exemplary fountain solutionapplicator;

FIG. 3 depicts a side view of the transparent roller forming acylindrical Fresnel lens and having an imaging device (e.g., a CCD)positioning inside the roller with an external measurement guide locatedadjacent the roller;

FIG. 3A depicts a view of a section of the cylindrical Fresnel lens ofthe transparent roller with the adjacent external measurement guidevisible through said lens;

FIG. 3B depicts an image at a first magnification captured by theimaging device through the Fresnel lens with no fluid on the outside ofthe transparent roller adjacent the external measurement guide;

FIG. 3C depicts an image at a second magnification captured by theimaging device through the Fresnel lens with a fluid of 0.95 mmthickness present on the outside of the transparent roller adjacent theexternal measurement guide;

FIG. 3D depicts an image at the second magnification captured by theimaging device through the Fresnel lens with a fluid of 2 mm thicknesspresent on the outside of the transparent roller adjacent the externalmeasurement guide;

FIG. 4A depicts an angled view of a Fresnel lens with no fluid disposedon the lens adjacent the external measurement guide;

FIG. 4B depicts an angled view of a Fresnel lens with a fluid disposedon the lens adjacent the external measurement guide;

FIG. 5A depicts a laboratory setup for a planar Fresnel lens with nofluid on its surface and with a laser light incident at 90° to the lensand being refracted to a location below along at a linear scale at a 60mm mark;

FIG. 5B depicts the same laboratory setup for a planar Fresnel lens butwith a fluid on its surface and with the laser light incident at 90° tothe lens and being refracted to a different location below along thelinear scale at a 30 mm mark;

FIG. 5C is an enlargement of the linear scale of FIG. 5A;

FIG. 5D is an enlargement of the linear scale of FIG. 5B;

FIG. 6 is a block diagram of a controller for executing instructions tocontrol the image forming device; and

FIG. 7 is a flowchart depicting the operation of an exemplary imageforming device.

DETAILED DESCRIPTION

Illustrative examples of the devices, systems, and methods disclosedherein are provided below. An embodiment of the devices, systems, andmethods may include any one or more, and any combination of, theexamples described below. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth below. Rather, these exemplary embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art.Accordingly, the exemplary embodiments are intended to cover allalternatives, modifications, and equivalents as may be included withinthe spirit and scope of the apparatuses, mechanisms and methods asdescribed herein.

We initially point out that description of well-known startingmaterials, processing techniques, components, equipment and otherwell-known details may merely be summarized or are omitted so as not tounnecessarily obscure the details of the present disclosure. Thus, wheredetails are otherwise well known, we leave it to the application of thepresent disclosure to suggest or dictate choices relating to thosedetails. The drawings depict various examples related to embodiments ofillustrative methods, apparatus, and systems for inking from an inkingmember to the reimageable surface of an imaging member.

When referring to any numerical range of values herein, such ranges areunderstood to include each and every number and/or fraction between thestated range minimum and maximum. For example, a range of 0.5-6% wouldexpressly include the endpoints 0.5% and 6%, plus all intermediatevalues of 0.6%, 0.7%, and 0.9%, all the way up to and including 5.95%,5.97%, and 5.99%. The same applies to each other numerical propertyand/or elemental range set forth herein, unless the context clearlydictates otherwise.

The modifier “about” used in connection with a quantity is inclusive ofthe stated value and has the meaning dictated by the context (forexample, it includes at least the degree of error associated with themeasurement of the particular quantity). When used with a specificvalue, it should also be considered as disclosing that value. Forexample, the term “about 2” also discloses the value “2” and the range“from about 2 to about 4” also discloses the range “from 2 to 4.”

The term “controller” or “control system” is used herein generally todescribe various apparatus such as a computing device relating to theoperation of one or more device that directs or regulates a process ormachine. A controller can be implemented in numerous ways (e.g., such aswith dedicated hardware) to perform various functions discussed herein.A “processor” is one example of a controller which employs one or moremicroprocessors that may be programmed using software (e.g., microcode)to perform various functions discussed herein. A controller may beimplemented with or without employing a processor, and also may beimplemented as a combination of dedicated hardware to perform somefunctions and a processor (e.g., one or more programmed microprocessorsand associated circuitry) to perform other functions. Examples ofcontroller components that may be employed in various embodiments of thepresent disclosure include, but are not limited to, conventionalmicroprocessors, application specific integrated circuits (ASIC s), andfield-programmable gate arrays (FPGAs).

Embodiments as disclosed herein may also include computer-readable mediafor carrying or having computer-executable instructions or datastructures stored thereon. Such computer-readable media can be anyavailable media that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation, suchcomputer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium which can be used to carry or store desiredprogram code means in the form of computer-executable instructions ordata structures. When information is transferred or provided over anetwork or another communications connection (either hardwired,wireless, or combination thereof) to a computer, the computer properlyviews the connection as a computer-readable medium. Thus, any suchconnection is properly termed a computer-readable medium. Combinationsof the above should also be included within the scope of thecomputer-readable media.

Computer-executable instructions include, for example, instructions anddata which cause a general purpose computer, special purpose computer,or special purpose processing device to perform a certain function orgroup of functions. Computer-executable instructions also includeprogram modules that are executed by computers in stand-alone or networkenvironments. Generally, program modules include routines, programs,objects, components, and data structures, and the like that performparticular tasks or implement particular abstract data types.Computer-executable instructions, associated data structures, andprogram modules represent examples of the program code means forexecuting steps of the methods disclosed herein. The particular sequenceof such executable instructions or associated data structures representsexamples of corresponding acts for implementing the functions describedtherein.

Although embodiments of the invention are not limited in this regard,discussions utilizing terms such as, for example, “processing,”“computing,” “calculating,” “determining,” “using,” “establishing”,“analyzing”, “checking”, or the like, may refer to operation(s) and/orprocess(es) of a controller, computer, computing platform, computingsystem, or other electronic computing device, that manipulate and/ortransform data represented as physical (e.g., electronic) quantitieswithin the computer's registers and/or memories into other datasimilarly represented as physical quantities within the computer'sregisters and/or memories or other information storage medium that maystore instructions to perform operations and/or processes.

The terms “media”, “print media”, “print substrate” and “print sheet”generally refers to a usually flexible physical sheet of paper, polymer,Mylar material, plastic, or other suitable physical print mediasubstrate, sheets, webs, etc., for images, whether precut or web fed.The listed terms “media”, “print media”, “print substrate” and “printsheet” may also include woven fabrics, non-woven fabrics, metal films,and foils, as readily understood by a skilled artisan.

The term “image forming device”, “printing device” or “printing system”as used herein may refer to a digital copier or printer, scanner, imageprinting machine, xerographic device, electrostatographic device,digital production press, document processing system, image reproductionmachine, bookmaking machine, facsimile machine, multi-function machine,or generally an apparatus useful in performing a print process or thelike and can include several marking engines, feed mechanism, scanningassembly as well as other print media processing units, such as paperfeeders, finishers, and the like. A “printing system” may handle sheets,webs, substrates, and the like. A printing system can place marks on anysurface, and the like, and is any machine that reads marks on inputsheets; or any combination of such machines.

The term “fountain solution” or “dampening fluid” refers to dampeningfluid that may coat or cover a surface of a structure (e.g., imagingmember, transfer roll) of an image forming device to affect connectionof a marking material (e.g., ink, toner, pigmented or dyed particles orfluid) to the surface. The fountain solution may include wateroptionally with small amounts of additives (e.g., isopropyl alcohol,ethanol) added to reduce surface tension as well as to lower evaporationenergy necessary to support subsequent laser patterning. Low surfaceenergy solvents, for example volatile silicone oils, can also serve asfountain solutions. Fountain solutions may also include wettingsurfactants, such as silicone glycol copolymers. The fountain solutionmay include D4 or D5 dampening fluid alone, mixed, and/or with wettingagents. The fountain solution may also include Isopar G, Isopar H,Dowsil OS20, Dowsil OS30, and mixtures thereof.

Inking systems or devices may be incorporated into a digital offsetimage forming device architecture so that the inking system is arrangedabout a central imaging plate, also referred to as an imaging member. Insuch a system, the imaging member is a rotatable imaging member,including a conformable blanket around a central drum with theconformable blanket including the reimageable surface. This blanketlayer has specific properties such as composition, surface profile, andso on so as to be well suited for receipt and carrying a layer of afountain solution. A surface of the imaging member is reimageable makingthe imaging member a digital imaging member. The surface is constructedof elastomeric materials and conformable. A paper path architecture maybe situated adjacent the imaging member to form a media transfer nip.

A layer of fountain solution may be applied to the surface of theimaging member by a dampening system. In a digital evaporation step,particular portions of the fountain solution layer deposited onto thesurface of the imaging member may be evaporated by a digital evaporationsystem. For example, portions of the fountain solution layer may bevaporized by an optical patterning subsystem such as a scanned,modulated laser that patterns the fluid solution layer to form a latentimage. In a vapor removal step, the vaporized fountain solution may becollected by a vapor removal device or vacuum to prevent condensation ofthe vaporized fountain solution back onto the imaging plate.

In an inking step, ink may be transferred from an inking system to thesurface of the imaging member such that the ink selectively resides inevaporated voids formed by the patterning subsystem in the fountainsolution layer to form an inked image. In an image transfer step, theinked image is then transferred to a print substrate such as paper viapressure at the media transfer nip.

In a digital variable printing process, previously imaged ink must beremoved from the imaging member surface to prevent ghosting. After animage transfer step, the surface of the imaging member may be cleaned bya cleaning system so that the printing process may be repeated. Forexample, tacky cleaning rollers may be used to remove residual ink andfountain solution from the surface of the imaging member.

A drawback of digital print processes is print quality sensitivity tothe amount of fountain solution deposited onto the imaging blanket. Itis estimated that a very thin layer of fountain solution (e.g., 30-100nm thickness range) is required on the blanket for optimal print processsetup. This makes measuring the fountain solution thickness on theimaging blanket most difficult.

FIG. 1 depicts an exemplary ink-based digital image forming device 10.The image forming device 10 may include dampening station 12 havingfountain solution applicator 14, optical patterning subsystem 16, inkingapparatus 18, and a cleaning device 20. The image forming device 10 mayalso include one or more rheological conditioning subsystems 22 asdiscussed, for example, in greater detail below. FIG. 1 shows thefountain solution applicator 14 arranged with a digital imaging member24 having a reimageable surface 26. While FIG. 1 shows components thatare formed as rollers, other suitable forms and shapes may beimplemented.

The imaging member surface 26 may be wear resistant and flexible. Thesurface 26 may be reimageable and conformable, having an elasticity anddurometer, and sufficient flexibility for coating ink over a variety ofdifferent media types having different levels of roughness. A thicknessof the reimageable surface layer may be, for example, about 0.5millimeters to about 4 millimeters. The surface 26 should have a weakadhesion force to ink, yet good oleophilic wetting properties with theink for promoting uniform inking of the reimageable surface andsubsequent transfer lift of the ink onto a print substrate.

The soft, conformable surface 26 of the imaging member 24 may include,for example, hydrophobic polymers such as silicones, partially or fullyfluorinated fluorosilicones and FKM fluoroelastomers. Other materialsmay be employed, including blends of polyurethanes, fluorocarbons,polymer catalysts, platinum catalyst, hydrosilyation catalyst, etc. Thesurface may be configured to conform to a print substrate on which anink image is printed. To provide effective wetting of fountain solutionssuch as water-based dampening fluid, the silicone surface need not behydrophilic, but may be hydrophobic. Wetting surfactants, such assilicone glycol copolymers, may be added to the fountain solution toallow the fountain solution to wet the reimageable surface 26. Theimaging member 24 may include conformable reimageable surface 26 of ablanket or belt wrapped around a roll or drum. The imaging membersurface 26 may be temperature controlled to aid in a printing operation.For example, the imaging member 24 may be cooled internally (e.g., withchilled fluid) or externally (e.g., via a blanket chiller roll 28 to atemperature (e.g., about 10° C.-60° C.) that may aid in the imageforming transfer and cleaning operations of image forming device 10.

The reimageable surface 26 or any of the underlying layers of thereimageable belt/blanket may incorporate a radiation sensitive fillermaterial that can absorb laser energy or other highly directed energy inan efficient manner. Examples of suitable radiation sensitive materialsare, for example, microscopic (e.g., average particle size less than 10micrometers) to nanometer sized (e.g., average particle size less than1000 nanometers) carbon black particles, carbon black in the form ofnano particles of, single or multi-wall nanotubes, graphene, iron oxidenano particles, nickel plated nano particles, etc., added to the polymerin at least the near-surface region. It is also possible that no fillermaterial is needed if the wavelength of a laser is chosen so to match anabsorption peak of the molecules contained within the fountain solutionor the molecular chemistry of the outer surface layer. As an example, a2.94 μm wavelength laser would be readily absorbed due to the intrinsicabsorption peak of water molecules at this wavelength.

The fountain solution applicator 14 may be configured to deposit a layerof fountain solution onto the imaging member surface 26 directly or viaan intermediate member (e.g., roller 30) of the dampening station 12.While not being limited to particular configuration, the fountainsolution applicator 14 may include a series of rollers, sprays or avaporizer (not shown) for uniformly wetting the reimageable surface 26with a uniform layer of fountain solution with the thickness of thelayer being controlled. The series of rollers may be considered asdampening rollers or a dampening unit, for uniformly wetting thereimageable surface 26 with a layer of fountain solution. The fountainsolution may be applied by fluid or vapor deposition to create a thinfluid layer 32 (e.g., between about 0.01 μm and about 1.0 μm inthickness, less than 5 μm, about 50 nm to 100 nm) of the fountainsolution for uniform wetting and pinning. The vaporizer may include aslot at its output across the imaging member 26 or intermediate roller30 to output vapor fountain solution to the imaging member surface 26.

FIG. 2 depicts another exemplary fountain solution applicator 14 thatmay apply a fountain solution layer directly onto the imaging membersurface 26. The fountain solution applicator 14 includes a supplychamber 62 that may be generally cylindrical defining an interior forcontaining fountain solution vapor therein. The supply chamber 62includes an inlet tube 64 in fluid communication with a fountainsolution supply (not shown), and a tube portion 66 extending to a closeddistal end 68 thereof. A supply channel 70 extends from the supplychamber 62 to adjacent the imaging member surface 26, with the supplychannel 70 defining an interior in communication with the interior ofthe supply chamber to enable flow of fountain solution vapor from thesupply chamber through the supply channel and out a supply channeloutlet slot 72 for deposition over the imaging member surface, where thefountain solution vapor condenses to a fluid on the imaging membersurface.

A vapor flow restriction border 74 extends from the supply channel 70adjacent the reimageable surface 26 to confine fountain solution vaporprovided from the supply channel outlet slot 72 to a condensation regiondefined by the restriction border and the adjacent reimageable surfaceto support forming a layer of fountain solution on the reimageablesurface via condensation of the fountain solution vapor onto thereimageable surface. The restriction border 74 defines the condensationregion over the surface 26 of the imaging member 24. The restrictionborder includes arc walls 76 that face the imaging member surface 26,and border wall 78 that extends from the arc walls towards the imagingmember surface. The reimageable surface 26 of the imaging member 24 mayhave a width W parallel to the supply channel 70 and supply channeloutlet slot 72, with the outlet slot having a width across the imagingmember configured to enable fountain solution vapor in the supplychamber interior to communicate with the imaging member surface 26across its width W.

As noted above, currently there is no way to measure how much fountainsolution is deposited on the imaging member blanket surface 26 inreal-time during a printing operation. One drawback in trying to measurethe thickness of fountain solution directly on the imaging blanket isthat the top surface of the blanket is coated with afluorosilicone/carbon black solution. The carbon black is added toabsorb the laser light during the imaging process. The carbon black alsomakes it very difficult to measure the fountain solution on the blanketduring image forming operations using a non-contact specular sensorbecause light is absorbed by the blanket. Such specular sensorsresearched as potential solutions have been very expensive. Anadditional drawback of the fluorosilicone/carbon black imaging membersurface is that any contact sensors scuff/abrade the surface causingdefects objectionable in the print. As a solution to the drawback, theinventors found that instead of measuring the thickness of fountainsolution directly on the imaging blanket, results of a current printingon a print substrate may be used to determine the fountain solutionthickness applied during the rendering of the current printing, and todetermine corrective action to modify fountain solution applicationduring subsequent printings to reach a desired thickness.

Referring back to FIG. 1, the inventors found that using a combination100 comprising a transparent roller 102, an internally-positionedimaging device 104, a heat source 106 and an external measurement guide108 can measure the thickness of fountain solution on the imaging membersurface in real-time during a printing operation. The location of thiscombination 100 is shown by the lead line arrow emanating from thecombination 100. The transparent roller 102 may comprise a clear orglass roller with an engineered surface of known surface roughness. Itshould be understood that the term “transparent” as used throughout thisSpecification means “light transmissive for purposes of carrying out theembodiment”. Although there are several ways to enable transfer of thefountain solution onto a controlled engineered surface (e.g., placingthe engineered surface roller near the blanket, and in an Inter-documentzone or any other non-printing area of the blanket), one preferredmethod uses a heat source 106 (e.g., an LED bar or laser) to evaporatethe dispensed fountain solution from the surface of the blanket and thento allow the evaporated fountain solution to condense on the transparentroller 102. The roller 102 comprises a surface 102A which comprises amicro Fresnel lens 102B engineered transparent surface that allows thefountain solution to wet the surface, thereby altering the opticalproperties. The fountain solution, e.g., D4 (Cyclosiloxane,Octamethylcyclotetrasiloxane), would be above 17° C. to be kept inliquid form. In this state, the fountain solution would wet the Fresnelsurface 102A. The fountain solution wets the surface to differentdegrees based on its thickness relative to the Fresnel ridge depth andchanges to the optical refraction through the lens varies with thicknessof the fountain solution film. The refraction is continuously measuredthrough the surface 102A of the roller 102 against the externalmeasurement guide 108 (e.g., the RCA television test pattern image). Asthe thickness of the film increases, the surface 102A becomes moresmooth, altering the Fresnel refractive properties and the angle of therefracted light is directly impacted. The thickness of the fountainsolution can then be determined via the direct change in lightrefraction through the roller 102. The present invention incorporates animaging device 104 (e.g., a CCD camera or image analysis system) forevaluation of an image through the transparent Fresnel collection roller102. Moreover, laser refraction through the roller 102 can also be usedto measure refraction differences as the fountain solution fluid coversthe Fresnel surface.

The external measurement guide 108 allows the imaging device 104 tocapture the distortion and clarity in an image due to the presence ofthe fountain solution on the transparent roller 102. By way of exampleonly, one type of external measurement guide 108 is similar to the RCAtelevision test pattern image which includes a variety of referencecharacters (lines, concentric circles, numerical characters, etc.) thatclarifies the distortion or clarity in the image. However, it should beunderstood that a variety of other reference characters could serve asthe external measurement guide 108.

One of the key aspects of the present invention is the recognition thatthe presence of the fountain solution affects how the image appearsthrough a lens and detecting that effect either through magnification,focus distance from a light source (e.g., laser, LED, etc.) and imagingdevice (e.g., CCD) and wherein that effect is correlated with fountainsolution thickness. Some examples are discussed of using a CCD foranalysis of the image distortion through the lens due to the FSthickness, or identifying the position of a laser from nominal andequating that to FS thickness based on refraction. As mentioned above,the image can be analyzed with regards to focus, magnification,measurements, etc., to identify the thickness of FS in relation to theFresnel ridge depth. Discussed below are several figures that usecylindrical and flat lenses. Modeling software testing performed on bothtypes of lens configurations yielded similar results. Thus, detection ofeither dimensional refraction (using either a laser or image to CCD), ordetection of magnification changes via dimensions measured via CCD, orfocal evaluation are all viable measurement schemes for ultimatelydetermining fountain solution thickness.

Examples of these various measurement schemes are shown in FIGS. 3A-3D,FIGS. 4A-4B and FIGS. 5A-5D. FIG. 3A depicts a view of a section of thecylindrical Fresnel lens 102B of the transparent roller 102 with theadjacent external measurement guide visible 108 through the lens 102B.FIG. 3B depicts an image at a first magnification captured by theimaging device 104 through the Fresnel lens 102B with no fountainsolution on the outside of the transparent roller 102 adjacent theexternal measurement guide 108. FIG. 3C depicts an image at a secondmagnification captured by the imaging device 104 through the Fresnellens 102B with a fountain solution of 0.95 mm thickness present on theoutside surface 102A of the transparent roller 102 adjacent the externalmeasurement guide 108. FIG. 3D depicts an image at the secondmagnification captured by the imaging device 104 through the Fresnellens 102B with a fountain solution of 2 mm thickness present on theoutside surface 102A of the transparent roller 102 adjacent the externalmeasurement guide 108. FIG. 4A depicts an angled view of a Fresnel lens102B with no fountain solution disposed on the lens 102B adjacent theexternal measurement guide 108. FIG. 4B depicts an angled view of theFresnel lens 102B with fountain solution disposed on the lens 102Badjacent the external measurement guide 108. FIG. 5A depicts alaboratory setup for a planar Fresnel lens with no fountain solution onits surface and with a laser light incident at 90° to the lens and beingrefracted to a location below along at a linear scale at a 60 mm mark;FIG. 5C is an enlargement of the linear scale of FIG. 5A. FIG. 5Bdepicts the same laboratory setup for a planar Fresnel lens but with afountain solution on its surface and with the laser light incident at90° to the lens and being refracted to a different location below alongthe linear scale at a 30 mm mark. FIG. 5D is an enlargement of thelinear scale of FIG. 5B.

Fountain solution layer 32 thickness quality control monitoring may beapplied on line during the printing process instead of periodic samplingafter the printing has been manufactured. This way fountain solutionflow rate adjustment can be made “on the fly”, reducing or eliminatingthe production of printings having undesired lessened quality.

Still referring to FIG. 1 the optical patterning subsystem 16 is locateddownstream the fountain solution applicator 14 in the printingprocessing direction to selectively pattern a latent image in the layerof fountain solution by image-wise patterning using for example, laserenergy. For example, the fountain solution layer is exposed to an energysource (e.g. a laser) that selectively applies energy to portions of thelayer to image-wise evaporate the fountain solution and create a latent“negative” of the ink image that is desired to be printed on a receivingsubstrate 34. Image areas are created where ink is desired, andnon-image areas are created where the fountain solution remains. Whilethe optical patterning subsystem 16 is shown as including laser emitter36, it should be understood that a variety of different systems may beused to deliver the optical energy to pattern the fountain solutionlayer.

A vapor vacuum 38 or air knife may be positioned downstream the opticalpatterning subsystem to collect vaporized fountain solution and thusavoid leakage of excess fountain solution into the environment.Reclaiming excess vapor prevents fountain solution from depositinguncontrollably prior to the inking apparatus 18 and imaging member 24interface. The vapor vacuum 38 may also prevent fountain solution vaporfrom entering the environment. Reclaimed fountain solution vapor can becondensed, filtered and reused as understood by a skilled artisan tohelp minimize the overall use of fountain solution by the image formingdevice 10.

Following patterning of the fountain solution layer by the opticalpatterning subsystem 16, the patterned layer over the reimageablesurface 26 is presented to the inking apparatus 18. The inker apparatus18 is positioned downstream the optical patterning subsystem 16 to applya uniform layer of ink over the layer of fountain solution and thereimageable surface layer 26 of the imaging member 24. The inkingapparatus 18 may deposit the ink to the evaporated pattern representingthe imaged portions of the reimageable surface 26, while ink depositedon the unformatted portions of the fountain solution will not adherebased on a hydrophobic and/or oleophobic nature of those portions. Theinking apparatus may heat the ink before it is applied to the surface 26to lower the viscosity of the ink for better spreading into imagedportion pockets of the reimageable surface. For example, one or morerollers 40 of the inking apparatus 18 may be heated, as well understoodby a skilled artisan. Inking roller 40 is understood to have a structurefor depositing marking material onto the reimageable surface layer 26,and may include an anilox roller or an ink nozzle. Excess ink may bemetered from the inking roller 40 back to an ink container 42 of theinker apparatus 18 via a metering member 44 (e.g., doctor blade, airknife).

Although the marking material may be an ink, such as a UV-curable ink,the disclosed embodiments are not intended to be limited to such aconstruct. The ink may be a UV-curable ink or another ink that hardenswhen exposed to UV radiation. The ink may be another ink having acohesive bond that increases, for example, by increasing its viscosity.For example, the ink may be a solvent ink or aqueous ink that thickenswhen cooled and thins when heated.

Downstream the inking apparatus 18 in the printing process directionresides ink image transfer station 46 that transfers the ink image fromthe imaging member surface 26 to a print substrate 34. The transferoccurs as the substrate 34 is passed through a transfer nip 48 betweenthe imaging member 24 and an impression roller 50 such that the inkwithin the imaged portion pockets of the reimageable surface 26 isbrought into physical contact with the substrate 34 and transfers viapressure at the transfer nip from the imaging member surface to thesubstrate as a print of the image.

Rheological conditioning subsystems 22 may be used to increase theviscosity of the ink at specific locations of the digital offset imageforming device 10 as desired. While not being limited to a particulartheory, rheological conditioning subsystem 22 may include a curingmechanism 52, such as a UV curing lamp (e.g., standard laser, UV laser,high powered UV LED light source), wavelength tunable photoinitiator, orother UV source, that exposes the ink to an amount of UV light (e.g., #of photons radiation) to at least partially cure the ink/coating to atacky or solid state. The curing mechanism may include various forms ofoptical or photo curing, thermal curing, electron beam curing, drying,or chemical curing. In the exemplary image forming device 10 depicted inFIG. 1, rheological conditioning subsystem 22 may be positioned adjacentthe substrate 34 downstream the ink image transfer station 46 to curethe ink image transferred to the substrate. Rheological conditioningsubsystems 22 may also be positioned adjacent the imaging member surface26 between the ink image transfer station 46 and cleaning device 20 as apreconditioner to harden any residual ink 54 for easier removal from theimaging member surface 26 that prepares the surface to repeat thedigital image forming operation.

This residual ink removal is most preferably undertaken without scrapingor wearing the imageable surface of the imaging member. Removal of suchremaining fluid residue may be accomplished through use of some form ofcleaning device 20 adjacent the surface 26 between the ink imagetransfer station 46 and the fountain solution applicator 14. Such acleaning device 20 may include at least a first cleaning member 56 suchas a sticky or tacky roller in physical contact with the imaging membersurface 26, with the sticky or tacky roller removing residual fluidmaterials (e.g., ink, fountain solution) from the surface. The sticky ortacky roller may then be brought into contact with a smooth roller (notshown) to which the residual fluids may be transferred from the stickyor tacky member, the fluids being subsequently stripped from the smoothroller by, for example, a doctor blade or other like device andcollected as waste. It is understood that the cleaning device 20 is oneof numerous types of cleaning devices and that other cleaning devicesdesigned to remove residual ink/fountain solution from the surface ofimaging member 24 are considered within the scope of the embodiments.For example, the cleaning device could include at least one roller,brush, web, belt, tacky roller, buffing wheel, etc., as well understoodby a skilled artisan.

In the image forming device 10, functions and utility provided by thedampening station 12, optical patterning subsystem 16, inking apparatus18, cleaning device 20, rheological conditioning subsystems 22, imagingmember 24 and combination 100 (discussed in detail below) may becontrolled, at least in part by controller 60. Such a controller 60 isshown in FIGS. 1 and 4, and may be further designed to receiveinformation and instructions from a workstation or other image inputdevices (e.g., computers, smart phones, laptops, tablets, kiosk) tocoordinate the image formation on the print substrate through thevarious subsystems such as the dampening station 12, patterningsubsystem 16, inking apparatus 18, imaging member 24 and combination 100as discussed in greater detail below and understood by a skilledartisan.

Using the combination 100, the controller 60 can determine the fountainsolution thickness resulting on the imaging member surface 26. Thecontroller 60 may calculate the fountain solution thickness and adjustthe fountain solution flow rate accordingly. The controller 60 may alsoaccess a lookup table (LUT) in data storage device 84 (FIG. 6) based onmeasured optical properties stored in the LUT. Further, the controller60 may access the LUT to determine an amount of modification of thefountain solution flow rate is needed to reach or maintain the desiredfountain solution layer thickness.

While measurement of the fountain solution thickness is not required forthe print process discussed herein including modifying fountain solutiondeposition in real time based on measured optical properties anddifferences in optical properties, the inventors found it is highlydesirable to measure signals that directly correlate to the fountainsolution thickness. To this end, the digital image forming device 10 cancontrol fountain solution thickness on the imaging member surface 26regardless of knowing the actual thickness. For example, upon knowingthe first set of optical properties (viz., no fountain solution on thetransparent roller 102), the controller 60 and imaging device 104 canmeasure the difference between the first set of optical properties andthe second set of optical properties (with the fountain solution layeron the transparent roller 102). The controller 60 may then compare thesedifferences to calculate a desired fountain solution layer thickness andmodify the fountain solution dispense or flow rate accordingly.

FIG. 6 illustrates a block diagram of the controller 60 for executinginstructions to automatically control the digital image forming device10 and components thereof. The exemplary controller 60 may provide inputto or be a component of a controller for executing the image formationmethod including controlling fountain solution thickness in a systemsuch as that depicted in FIGS. 1-5C, and described in greater detailbelow.

The exemplary controller 60 may include an operating interface 80 bywhich a user may communicate with the exemplary control system. Theoperating interface 80 may be a locally-accessible user interfaceassociated with the digital image forming device 10. The operatinginterface 80 may be configured as one or more conventional mechanismcommon to controllers and/or computing devices that may permit a user toinput information to the exemplary controller 60. The operatinginterface 80 may include, for example, a conventional keyboard, atouchscreen with “soft” buttons or with various components for use witha compatible stylus, a microphone by which a user may provide oralcommands to the exemplary controller 60 to be “translated” by a voicerecognition program, or other like device by which a user maycommunicate specific operating instructions to the exemplary controller.The operating interface 80 may be a part or a function of a graphicaluser interface (GUI) mounted on, integral to, or associated with, thedigital image forming device 10 with which the exemplary controller 60is associated.

The exemplary controller 60 may include one or more local processors 82for individually operating the exemplary controller 60 and for carryinginto effect control and operating functions for image formation onto aprint substrate 34, including rendering digital images, measuringchanges in optical properties to determine thickness of fountainsolution applied by a fountain solution applicator on an imaging membersurface and/or determine image forming device real-time image formingmodifications for subsequent printings. For example, in real-time duringthe printing of a print job, based on the measured optical properties ofthe fountain solution thickness, processors 82 may adjust image forming(e.g., fountain solution deposition flow rate) to reach or maintain apreferred fountain solution thickness on the imaging member surface forsubsequent (e.g., next) printings of the print job with the digitalimage forming device 10 with which the exemplary controller may beassociated. Processor(s) 82 may include at least one conventionalprocessor or microprocessor that interprets and executes instructions todirect specific functioning of the exemplary controller 60, and controladjustments of the image forming process with the exemplary controller.

The exemplary controller 60 may include one or more data storage devices84. Such data storage device(s) 84 may be used to store data oroperating programs to be used by the exemplary controller 60, andspecifically the processor(s) 82. Data storage device(s) 84 may be usedto store information regarding, for example, digital image information,printed image response data, fountain solution thickness correspondingto optical property changes, and other fountain solution depositioninformation with which the digital image forming device 10 isassociated. Measured optical properties and fountain solution thicknessdata may be devolved into data to generate a recurring, continuous orclosed loop feedback fountain solution deposition rate modification inthe manner generally described by examples herein.

The data storage device(s) 84 may include a random access memory (RAM)or another type of dynamic storage device that is capable of storingupdatable database information, and for separately storing instructionsfor execution of image correction operations by, for example,processor(s) 82. Data storage device(s) 84 may also include a read-onlymemory (ROM), which may include a conventional ROM device or anothertype of static storage device that stores static information andinstructions for processor(s) 82. Further, the data storage device(s) 84may be integral to the exemplary controller 60, or may be providedexternal to, and in wired or wireless communication with, the exemplarycontroller 60, including as cloud-based data storage components.

The data storage device(s) 84 may include non-transitorymachine-readable storage medium used to store the device queue managerlogic persistently. While a non-transitory machine-readable storagemedium is may be discussed as a single medium, the term“machine-readable storage medium” should be taken to include a singlemedium or multiple media (e.g., a centralized or distributed database,and/or associated caches and servers) that store one or more sets ofinstructions. The term “machine-readable storage medium” shall also betaken to include any medium that is capable of storing or encoding a setof instruction for execution by the controller 60 and that causes thedigital image forming device 10 to perform any one or more of themethodologies of the present invention. The term “machine-readablestorage medium” shall accordingly be taken to include, but not belimited to, solid-state memories, and optical and magnetic media.

The exemplary controller 60 may include at least one data output/displaydevice 86, which may be configured as one or more conventionalmechanisms that output information to a user, including, but not limitedto, a display screen on a GUI of the digital image forming device 10 orassociated image forming device with which the exemplary controller 60may be associated. The data output/display device 86 may be used toindicate to a user a status of the digital image forming device 10 withwhich the exemplary controller 60 may be associated including anoperation of one or more individually controlled components at one ormore of a plurality of separate image processing stations or subsystemsassociated with the image forming device.

The exemplary controller 60 may include one or more separate externalcommunication interfaces 88 by which the exemplary controller 60 maycommunicate with components that may be external to the exemplarycontrol system such as the transparent roller 102, imaging device 104and the heat source 106 that can monitor fountain solution layer 32thickness. At least one of the external communication interfaces 88 maybe configured as an input port to support connecting an external CAD/CAMdevice storing modeling information for execution of the controlfunctions in the image formation and correction operations. Any suitabledata connection to provide wired or wireless communication between theexemplary controller 60 and external and/or associated components iscontemplated to be encompassed by the depicted external communicationinterface 88.

The exemplary controller 60 may include an image forming control device90 that may be used to control an image correction process includingfountain solution deposition rate control and modification to renderimages on imaging member surface 26 having a desired fountain solutionthickness. For example, the image forming control device 90 may renderdigital images on the reimageable surface 26 having a desired fountainsolution thickness from fountain solution flow adjusted automatically inreal-time based on capacitive measurements of prior printings of thesame print job. The image forming control device 90 may operate as apart or a function of the processor 82 coupled to one or more of thedata storage devices 84 and the digital image forming device 10 (e.g.,optical patterning subsystem 16, inking apparatus 18, dampening station12), or may operate as a separate stand-alone component module orcircuit in the exemplary controller 60.

All of the various components of the exemplary controller 60, asdepicted in FIG. 6, may be connected internally, and to the digitalimage forming device 10, associated image forming apparatuses downstreamthe image forming device and/or components thereof, by one or moredata/control busses 92. These data/control busses 92 may provide wiredor wireless communication between the various components of the imageforming device 10 and any associated image forming apparatus, whetherall of those components are housed integrally in, or are otherwiseexternal and connected to image forming devices with which the exemplarycontroller 60 may be associated.

It should be appreciated that, although depicted in FIG. 6 as anintegral unit, the various disclosed elements of the exemplarycontroller 60 may be arranged in any combination of subsystems asindividual components or combinations of components, integral to asingle unit, or external to, and in wired or wireless communication withthe single unit of the exemplary control system. In other words, nospecific configuration as an integral unit or as a support unit is to beimplied by the depiction in FIG. 6. Further, although depicted asindividual units for ease of understanding of the details provided inthis disclosure regarding the exemplary controller 60, it should beunderstood that the described functions of any of theindividually-depicted components, and particularly each of the depictedcontrol devices, may be undertaken, for example, by one or moreprocessors 82 connected to, and in communication with, one or more datastorage device(s) 84.

The disclosed embodiments may include an exemplary method forcontrolling fountain solution thickness on an imaging member surface ofa rotating imaging member in a digital image forming device 10. FIG. 7illustrates a flowchart of such an exemplary method. As shown in FIG. 7,operation of the method commences at Step S200 and proceeds to StepS202.

At Step S202, the fountain solution (FS) is dispensed from the FSapplicator 14 to the rotating imaging member blanket 26. Operation ofthe method proceeds to Step S204.

At Step S204, the transparent roller 102 with a predetermined surfaceroughness is positioned adjacent the rotating imaging member blanket 26;the roller 102 includes the imaging device 104 therein so as to capturelight passing through the roller surface 102A which acts as a lens 102B.With no FS on the transparent roller 102, the imaging device 104 andcontroller 60 define a first set of optical properties. Operationproceeds to Step S206.

At Step S206, the FS dispensed on the blanket 26 is evaporated off theblanket 26 using a heat source 106 and is then condensed onto thetransparent roller surface 102A to effect the transfer of the FS. Assuch, the imaging device 104 in combination with the externalmeasurement guide 108 provide the controller 60 with a second set ofoptical properties based on the light passing through the FS film now onthe transparent roller lens 102B.

Operation of the method proceeds to Step S208, where the controller orprocessor 60 thereof compares the difference in the first and second setof optical properties to calculate a thickness of the FS. The controller60 may store and average the measured differences in optical propertiesto define fountain solution layer thicknesses over a period and comparethe average to a predefined target or desirable fountain solutionthickness. Using average measurements may account for a small variancein fountain solution thickness across successive printings allowedwithin manufacturing tolerances. The predefined target fountain solutionthickness information may be stored in data storage device 84 asdepicted in FIG. 6 or as a lookup table.

Operation of the method proceeds to Steps S210-S212, where thecontroller 60 modifies the fountain solution dispense rate based on thecomparison for subsequent printing using the modified fountain solutiondispense rate. Operation may cease at Step S214 or may continue byrepeating back to Step S210 where the fountain solution applicator 14applies a subsequent fountain solution layer at the modified fountainsolution dispense rate onto the imaging member surface as desired.

The exemplary depicted sequence of executable method steps representsone example of a corresponding sequence of acts for implementing thefunctions described in the steps. The exemplary depicted steps may beexecuted in any reasonable order to carry into effect the objectives ofthe disclosed embodiments. No particular order to the disclosed steps ofthe method is necessarily implied by the depiction in FIG. 7, and theaccompanying description, except where any particular method step isreasonably considered to be a necessary precondition to execution of anyother method step. Individual method steps may be carried out insequence or in parallel in simultaneous or near simultaneous timing.Additionally, not all of the depicted and described method steps need tobe included in any particular scheme according to disclosure.

Those skilled in the art will appreciate that other embodiments of thedisclosed subject matter may be practiced with many types of imageforming elements common to offset inking system in many differentconfigurations. For example, although digital lithographic systems andmethods are shown in the discussed embodiments, the examples may applyto analog image forming systems and methods, including analog offsetinking systems and methods. It should be understood that these arenon-limiting examples of the variations that may be undertaken accordingto the disclosed schemes. In other words, no particular limitingconfiguration is to be implied from the above description and theaccompanying drawings.

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also,various presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art.

What is claimed is:
 1. A method of controlling fountain solutionthickness on an imaging member surface of a rotating imaging member inan image forming device, comprising: a) dispensing fountain solutionfrom an applicator onto said rotating imaging member; b) positioning atransparent roller having a surface with a predetermined roughnessadjacent said rotating imaging member, said transparent rollercomprising an imaging device positioned within said transparent rollerfor capturing light passing through said surface, said surface forming alens and wherein light passing through said lens to said imaging deviceis defined by a first set of optical properties; c) transferring saiddispensed fountain solution from said rotating imaging member onto saidsurface of said transparent roller to allow said transferred fountainsolution to wet said surface of said transparent roller to alter saidfirst set of optical properties to a second set of optical properties;d) comparing said second set of optical properties with said first setof optical properties to calculate a thickness of said dispensedfountain solution on said transparent roller; e) modifying the fountainsolution dispense rate based on the calculated thickness; and f)applying a subsequent fountain solution layer at the modified fountainsolution dispense rate onto the imaging member surface for rendering asubsequent printing.
 2. The method of claim 1, wherein said lenscomprises a micro Fresnel lens.
 3. The method of claim 2 wherein saidstep of allowing said transferred fountain solution to wet the surfaceof said transparent roller permits said dispensed fountain solution towet said surface to different degrees based on the thickness of saiddispensed fountain solution relative to Fresnel ridge depth.
 4. Themethod of claim 2, wherein said step of comparing said second set ofoptical properties with said first set of optical properties tocalculate a thickness of said dispensed fountain solution on saidtransparent roller comprises continually measuring through said lens toan externally-located measurement surface and wherein as the thicknessof said dispensed fountain solution increases, the lens becomes moresmooth, thereby altering Fresnel refractive properties and an angle ofrefracted light.
 5. The method of claim 1, wherein said step oftransferring said dispensing fountain solution onto said transparentroller comprises: (b1) positioning said transparent roller closelyadjacent said rotating imaging member; (b2) activating a heat source toevaporate the fountain solution from the surface of the rotating imagingmember; and (b3) condensing said evaporated fountain solution onto saidtransparent roller.
 6. The method of claim 5, wherein said heat sourcecomprises an LED bar.
 7. The method of claim 5, wherein said heat sourcecomprises a laser.
 8. The method of claim 1 wherein said imaging devicecomprises a CCD camera.
 9. The method of claim 1, wherein the step ofrendering the subsequent printing includes the image forming deviceapplying the subsequent fountain solution layer at the modified fountainsolution dispense rate onto the imaging member surface, vaporizing in animage wise fashion a portion of the subsequent fountain solution layerto form a subsequent latent image, applying ink onto the subsequentlatent image over the imaging member surface, and transferring theapplied ink from the imaging member surface to a subsequent printsubstrate.
 10. The method of claim 1, wherein said transparent roller isoperated at a rotational speed slower than a rotational speed of saidimaging member.
 11. An image forming device controlling fountainsolution thickness on an imaging member surface of a rotating imagingmember, comprising: a fountain solution applicator configured to apply afountain solution fluid layer at a dispense rate onto the imaging membersurface in an image making direction for rendering a printing, atransparent roller having a surface of a predetermined roughness andwhere said transparent roller further comprises an imaging devicepositioned within said transparent roller for capturing light passingthrough said surface, said surface forming a lens and wherein lightpassing through said lens to said imaging device is defined by a firstset of optical properties; a heat source for evaporating said dispensedfountain solution from said imaging member to said transparent rollerwhere said evaporated fountain solution then condenses onto saidtransparent roller, said condensed fountain solution wetting saidsurface to alter said first set of optical properties to a second set ofoptical properties; a controller in communication with said imagingdevice to compare said first set of optical properties with said secondset of optical properties to determine a thickness of said dispensedfountain solution on said transparent roller and in accordance therewithto define a modified fountain solution dispense rate to provide anoptimum thickness of said dispensed fountain solution thickness; saidfountain solution applicator configured to apply a subsequent fountainsolution layer at the modified fountain solution dispense rate onto theimaging member surface for rendering a subsequent printing.
 12. Thedevice of claim 11, wherein said lens comprises a micro Fresnel lens.13. The device of claim 12, wherein said wetted surface of saidtransparent roller permits said dispensed fountain solution to wet saidsurface to different degrees based on the thickness of said dispensedfountain solution relative to Fresnel ridge depth.
 14. The device ofclaim 12, wherein imaging device and said controller continuallymeasuring through said lens to an externally-located measurement surfaceand wherein as the thickness of said dispensed fountain solutionincreases, the lens becomes more smooth, thereby altering Fresnelrefractive properties and an angle of refracted light.
 15. The device ofclaim 11, wherein said heat source comprises an LED bar.
 16. The deviceof claim 11, wherein said heat source comprises a laser.
 17. The deviceof claim 11, wherein said imaging device comprises a CCD camera.
 18. Thedevice of claim 11, wherein said imaging device comprises a laser. 19.The device of claim 11 wherein said subsequent printing includes theimage forming device applying the subsequent fountain solution layer atthe modified fountain solution dispense rate onto the imaging membersurface, vaporizing in an image wise fashion a portion of the subsequentfountain solution layer to form a subsequent latent image, applying inkonto the subsequent latent image over the imaging member surface, andtransferring the applied ink from the imaging member surface to asubsequent print substrate.
 20. The device of claim 11 wherein saidtransparent roller is operated at a rotational speed slower than arotational speed of said imaging member.